Calculus Examples

$f (x) = {(\frac{x - 4}{x + 2})}^{3}$

Step 1

Differentiate using the chain rule, which states that $\frac{d}{d x} [f (g (x))]$ is $f' (g (x)) g' (x)$ where $f (x) = x^{3}$ and $g (x) = \frac{x - 4}{x + 2}$ .

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Step 1.1

To apply the Chain Rule, set $u$ as $\frac{x - 4}{x + 2}$ .

$\frac{d}{d u} [u^{3}] \frac{d}{d x} [\frac{x - 4}{x + 2}]$

Step 1.2

Differentiate using the Power Rule which states that $\frac{d}{d u} [u^{n}]$ is $n u^{n - 1}$ where $n = 3$ .

$3 u^{2} \frac{d}{d x} [\frac{x - 4}{x + 2}]$

Step 1.3

Replace all occurrences of $u$ with $\frac{x - 4}{x + 2}$ .

$3 {(\frac{x - 4}{x + 2})}^{2} \frac{d}{d x} [\frac{x - 4}{x + 2}]$

Step 2

Differentiate using the Quotient Rule which states that $\frac{d}{d x} [\frac{f (x)}{g (x)}]$ is $\frac{g (x) \frac{d}{d x} [f (x)] - f (x) \frac{d}{d x} [g (x)]}{{g (x)}^{2}}$ where $f (x) = x - 4$ and $g (x) = x + 2$ .

$3 {(\frac{x - 4}{x + 2})}^{2} \frac{(x + 2) \frac{d}{d x} [x - 4] - (x - 4) \frac{d}{d x} [x + 2]}{{(x + 2)}^{2}}$

Step 3

Differentiate.

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Step 3.1

By the Sum Rule, the derivative of $x - 4$ with respect to $x$ is $\frac{d}{d x} [x] + \frac{d}{d x} [- 4]$ .

$3 {(\frac{x - 4}{x + 2})}^{2} \frac{(x + 2) (\frac{d}{d x} [x] + \frac{d}{d x} [- 4]) - (x - 4) \frac{d}{d x} [x + 2]}{{(x + 2)}^{2}}$

Step 3.2

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$3 {(\frac{x - 4}{x + 2})}^{2} \frac{(x + 2) (1 + \frac{d}{d x} [- 4]) - (x - 4) \frac{d}{d x} [x + 2]}{{(x + 2)}^{2}}$

Step 3.3

Since $- 4$ is constant with respect to $x$ , the derivative of $- 4$ with respect to $x$ is $0$ .

$3 {(\frac{x - 4}{x + 2})}^{2} \frac{(x + 2) (1 + 0) - (x - 4) \frac{d}{d x} [x + 2]}{{(x + 2)}^{2}}$

Step 3.4

Simplify the expression.

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Step 3.4.1

Add $1$ and $0$ .

$3 {(\frac{x - 4}{x + 2})}^{2} \frac{(x + 2) \cdot 1 - (x - 4) \frac{d}{d x} [x + 2]}{{(x + 2)}^{2}}$

Step 3.4.2

Multiply $x + 2$ by $1$ .

$3 {(\frac{x - 4}{x + 2})}^{2} \frac{x + 2 - (x - 4) \frac{d}{d x} [x + 2]}{{(x + 2)}^{2}}$

Step 3.5

By the Sum Rule, the derivative of $x + 2$ with respect to $x$ is $\frac{d}{d x} [x] + \frac{d}{d x} [2]$ .

$3 {(\frac{x - 4}{x + 2})}^{2} \frac{x + 2 - (x - 4) (\frac{d}{d x} [x] + \frac{d}{d x} [2])}{{(x + 2)}^{2}}$

Step 3.6

Differentiate using the Power Rule which states that $\frac{d}{d x} [x^{n}]$ is $n x^{n - 1}$ where $n = 1$ .

$3 {(\frac{x - 4}{x + 2})}^{2} \frac{x + 2 - (x - 4) (1 + \frac{d}{d x} [2])}{{(x + 2)}^{2}}$

Step 3.7

Since $2$ is constant with respect to $x$ , the derivative of $2$ with respect to $x$ is $0$ .

$3 {(\frac{x - 4}{x + 2})}^{2} \frac{x + 2 - (x - 4) (1 + 0)}{{(x + 2)}^{2}}$

Step 3.8

Combine fractions.

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Step 3.8.1

Add $1$ and $0$ .

$3 {(\frac{x - 4}{x + 2})}^{2} \frac{x + 2 - (x - 4) \cdot 1}{{(x + 2)}^{2}}$

Step 3.8.2

Multiply $- 1$ by $1$ .

$3 {(\frac{x - 4}{x + 2})}^{2} \frac{x + 2 - (x - 4)}{{(x + 2)}^{2}}$

Step 3.8.3

Combine $\frac{x + 2 - (x - 4)}{{(x + 2)}^{2}}$ and $3$ .

$\frac{(x + 2 - (x - 4)) \cdot 3}{{(x + 2)}^{2}} {(\frac{x - 4}{x + 2})}^{2}$

Step 3.8.4

Move $3$ to the left of $x + 2 - (x - 4)$ .

$\frac{3 \cdot (x + 2 - (x - 4))}{{(x + 2)}^{2}} {(\frac{x - 4}{x + 2})}^{2}$

Step 4

Simplify.

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Step 4.1

Apply the product rule to $\frac{x - 4}{x + 2}$ .

$\frac{3 (x + 2 - (x - 4))}{{(x + 2)}^{2}} \cdot \frac{{(x - 4)}^{2}}{{(x + 2)}^{2}}$

Step 4.2

Apply the distributive property.

$\frac{3 (x + 2 - x - - 4)}{{(x + 2)}^{2}} \cdot \frac{{(x - 4)}^{2}}{{(x + 2)}^{2}}$

Step 4.3

Apply the distributive property.

$\frac{3 x + 3 \cdot 2 + 3 (- x) + 3 (- - 4)}{{(x + 2)}^{2}} \cdot \frac{{(x - 4)}^{2}}{{(x + 2)}^{2}}$

Step 4.4

Combine terms.

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Step 4.4.1

Multiply $3$ by $2$ .

$\frac{3 x + 6 + 3 (- x) + 3 (- - 4)}{{(x + 2)}^{2}} \cdot \frac{{(x - 4)}^{2}}{{(x + 2)}^{2}}$

Step 4.4.2

Multiply $- 1$ by $3$ .

$\frac{3 x + 6 - 3 x + 3 (- - 4)}{{(x + 2)}^{2}} \cdot \frac{{(x - 4)}^{2}}{{(x + 2)}^{2}}$

Step 4.4.3

Multiply $- 1$ by $- 4$ .

$\frac{3 x + 6 - 3 x + 3 \cdot 4}{{(x + 2)}^{2}} \cdot \frac{{(x - 4)}^{2}}{{(x + 2)}^{2}}$

Step 4.4.4

Multiply $3$ by $4$ .

$\frac{3 x + 6 - 3 x + 12}{{(x + 2)}^{2}} \cdot \frac{{(x - 4)}^{2}}{{(x + 2)}^{2}}$

Step 4.4.5

Subtract $3 x$ from $3 x$ .

$\frac{0 + 6 + 12}{{(x + 2)}^{2}} \cdot \frac{{(x - 4)}^{2}}{{(x + 2)}^{2}}$

Step 4.4.6

Add $0$ and $6$ .

$\frac{6 + 12}{{(x + 2)}^{2}} \cdot \frac{{(x - 4)}^{2}}{{(x + 2)}^{2}}$

Step 4.4.7

Add $6$ and $12$ .

$\frac{18}{{(x + 2)}^{2}} \cdot \frac{{(x - 4)}^{2}}{{(x + 2)}^{2}}$

Step 4.4.8

Multiply $\frac{18}{{(x + 2)}^{2}}$ by $\frac{{(x - 4)}^{2}}{{(x + 2)}^{2}}$ .

$\frac{18 {(x - 4)}^{2}}{{(x + 2)}^{2} {(x + 2)}^{2}}$

Step 4.4.9

Multiply ${(x + 2)}^{2}$ by ${(x + 2)}^{2}$ by adding the exponents.

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Step 4.4.9.1

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$\frac{18 {(x - 4)}^{2}}{{(x + 2)}^{2 + 2}}$

Step 4.4.9.2

Add $2$ and $2$ .

$\frac{18 {(x - 4)}^{2}}{{(x + 2)}^{4}}$